export const a = 1;


/**
 * 实现一个通用First<T>，它接受一个数组T并返回它的第一个元素的类型。
 * 
 * https://github.com/type-challenges/type-challenges/tree/main/questions/00014-easy-first
 */
type arr1 = ['a', 'b', 'c']
type arr2 = [3, 2, 1]

type First<T extends  unknown[]> = T[0]


type head1 = First<arr1> // expected to be 'a'
type head2 = First<arr2> // expected to be 3